allenwb

Array.prototype.fill = function fill(value,start=0, end=this.length) {
  /*
    Every element of array from start up to but not including end are assigned value.
    start and end are interpretation the same as for slice,
        negative start or stop indices are converted to positive indices relative to the lenth of the array.
        
    
    If end<=start no elements are modified.
    If end>this.length and this.length is read-only a range error is thrown and no elements are modified.
    If end>this.length and this.length is not read-only, this.length is set to end.

allenwb

Array.prototype.transfer = function transfer(target=0,start=0, end=this.length, fill=missingMarker) {
/*
The sequence of array elements of array from start up to but not including end are transferred within 
the array to the span starting at the index target. The length of the array is not modified.


start and end are interpretation the same as for slice,
negative start, end, and target indices are converted to positive indices relative to the lenth of the array.
If end<=start no elements are transfered.
If end>this.length or target+(end-start)>this.length a range error is thrown and no elements are modified.

allenwb

function *forin(obj) {
  let processed = new Set();
  while (obj!==null) {
    let here = Object.getOwnPropertyNames(obj);
    for (let i=0; i<here.length; i++) {
      let name = here[i];
      if (processed.has(name)) continue;
      processed.add(name);
      let desc = Object.getOwnPropertyDescriptor(obj,name);
      if (desc && desc.enumerable) yield name;

allenwb

function mapReviver(key, value) {
   if (typeof value != "object") return value;
   switch (value["<kind>"]){
      case undefined: return value;
      case "Map": {
         let newValue = new Map;
         let mapData = value["<mapData>"];
         if (!mapData) return value;
         mapData.forEach(e=>newValue.set(e[0], e[1]));
         return newValue;

allenwb

New ES6 Constructor Semantics and Usage Examples

Manual super: Alternative Design where subclass constructors do not automatically call superclass constructors

This Gist presents a new design of class-based object construction in ES6 that does not require use of the two-phase @@create protocol.

One of the characteristics of this proposal is that subclass constructors must explicitly super invoke their superclass's constructor if they wish to use the base class' object allocation and initialization logic.

An alternative version of this design automatically invokes the base constructor in most situations.